#!/usr/bin/python

import random

START_LEN = 120
MID_LEN = 180
END_LEN = 120

def print_ideal():
    while True:
        seq = ''.join(random.choice('actg') for i in xrange( START_LEN )) \
            + 'act' * (MID_LEN / 3) \
            + ''.join(random.choice('actg') for i in range( END_LEN )) 
        print seq

def print_shift():
    while True:
        shift_index = MID_LEN / 2
        seq = ''.join(random.choice('actg') for i in xrange( START_LEN )) \
            + 'act' * (MID_LEN / 3) \
            + ''.join(random.choice('actg') for i in range( END_LEN ))
        seq = seq[:START_LEN+shift_index] + 'g' + seq[START_LEN+shift_index:]
        print seq

if __name__ == "__main__":
    print_shift()

